Integrated circuits are manufactured on thin silicon wafers which are circular in shape and typically range in diameter from four to twelve inches. The wafers undergo many different processes during the overall manufacturing cycle, and each process may be performed by a different machine in cleanrooms. It is critically important during the entire cycle that the wafers be kept as clean as possible, and that they be handled as carefully as possible to avoid damaging the integrated circuits thereon. Therefore, wafers must be transported with the utmost care from machine to machine within a clean-room manufacturing facility.
Much of the transporting of wafers during the manufacturing process is performed by automated transporters. Robotic arms remove the wafers from each processing machine and place them in a transportation rack. The rack is moved to the next processing machine where another robotic arm removes the wafers from the rack and places them in the machine. Generally, if all components maintain proper alignment in the wafer-transportation system, the entire cycle can be handled automatically. Sometimes, however, it is necessary for human intervention and, therefore, the manual grasping and transportation of wafers. Vacuum wands are used to manually transfer wafers, masks, and t he like.
Current state-of-the-art cleanrooms are designed to exclude particles greater than .about.0.2 micron diameter in ambient air. However, a s the minimum electronic feature size decreases, so does the critical size of "killer particles." Since it is estimated that there are about 100 times more 0.05 micron particles than there are 0.2 micron particles in, for example, a Class 100 cleanroom, it is more difficult to prevent such small particles from contaminating sensitive surfaces.